Stubley Samuel J, Cayre Olivier J, Murray Brent S, Celigueta Torres Isabel
Food Colloids & Bioprocessing Group, School of Food Science & Nutrition, University of Leeds, LS2 9JT, UK.
Colloid and Polymer Engineering Group, School of Chemical & Process Engineering, University of Leeds, LS2 9JT, UK.
J Colloid Interface Sci. 2022 Dec 15;628(Pt A):684-695. doi: 10.1016/j.jcis.2022.07.147. Epub 2022 Jul 28.
A novel range of microgel particles of different internal cross-linking densities can be created by covalently cross-linking sugar beet pectin (SBP) with the enzyme laccase and mechanically breaking down the subsequent parent hydrogels to sugar beet pectin microgels (SBPMG) via shearing. The bulk rheological properties of suspensions of the different SBPMG are expected to depend on the microgel morphology, elasticity (crosslinking density) and volume fraction respectively.
The rheology of both dilute and concentrated dispersions of SBPMG were studied in detail via capillary viscometry and shear rheometry, supplemented by information on particle size and shape from static light scattering, confocal microscopy and electron microscopy.
For dilute suspensions of SBPMG, data for viscosity versus effective volume fraction (ɸ) falls on a 'master' curve for all 3 types of SBPMG. In the more concentrated regime, the softer microgels allow greater packing and interpenetration and give lower viscosities at the same ɸ, but all 3 types of microgel give much higher viscosities than the equivalent concentration of 'non-microgelled' pectin. The firmer microgels can be concentrated to achieve elasticities equivalent to the original parent hydrogel. All SBPMG suspensions were extremely shear thinning but showed virtually no time-dependence.
通过将甜菜果胶（SBP）与漆酶共价交联，并通过剪切将随后的母体水凝胶机械分解为甜菜果胶微凝胶（SBPMG），可以制备出一系列具有不同内部交联密度的新型微凝胶颗粒。预计不同SBPMG悬浮液的整体流变特性分别取决于微凝胶的形态、弹性（交联密度）和体积分数。
通过毛细管粘度测定法和剪切流变测定法详细研究了SBPMG稀分散体和浓分散体的流变学，并辅以静态光散射、共聚焦显微镜和电子显微镜提供的有关颗粒大小和形状的信息。
对于SBPMG的稀悬浮液，所有3种类型的SBPMG的粘度与有效体积分数（ɸ）的数据都落在一条“主”曲线上。在浓度更高的体系中，较软的微凝胶允许更大程度的堆积和相互渗透，并且在相同的ɸ下具有较低的粘度，但所有3种类型的微凝胶的粘度都比同等浓度的“非微凝胶化”果胶高得多。较硬的微凝胶可以浓缩以实现与原始母体水凝胶相当的弹性。所有SBPMG悬浮液都表现出极强的剪切变稀特性，但几乎没有时间依赖性。
